Transferable Approach of Semi-Empirical Modeling of Disordered Mixed Halide Hybrid Perovskites CH3NH3Pb(I1-xBrx)3: Prediction of Thermodynamic Properties, Phase Stability and Deviations from Vegard’s Lawстатья
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Аннотация:We report here a novel approach on computational investigation of the CH3NH3Pb(I1–xBrx)3 solid solutions using the classical interatomic potential method in disorder supercells. The developed interatomic potential set is used to calculate Gibbs free energy and geometrical parameters for orthorhombic, tetragonal and cubic modifications of perovskites with various I/Br ratio at different temperatures. The obtained results are in a good agreement with experimental data and predict a tetragonal to cubic phase transition at Br content of ∼0.2 and experimentally observed deviation from the Vegard’s law for the CH3NH3Pb(I1–xBrx)3 disordered solid solution. In addition, we calculated thermal dependency of Gibbs free energy and therefore provided a thermodynamic rationale for a large miscibility gap in orthorhombic and tetragonal modifications of CH3NH3Pb(I1–xBrx)3 at low temperatures. This, in turn, provides thermodynamic driving force for phase segregation of the mixed-halide perovskites, which was proved experimentally.